Kinetic Modeling of Film Growth Rate in Atomic Layer Deposition

Abstract

A kinetic model of film growth rate in atomic layer deposition (ALD) has been studied analytically. This model is derived separately for the transient region and converged regions, and combines to describe the film growth kinetics in both regions. During the initial transient stage of ALD, the outermost surface is converted gradually from the substrate into the film as deposition proceeds. Therefore, the digital characteristic of controlling film thickness by the number of deposition cycles in ALD is lost in this region. Hence, it is necessary to consider the transient region in combination with the converged region in order to predict accurately the film thickness, especially when the thickness is less than 10 nm. Moreover, by utilizing the physical parameters which are extracted from fitting the proposed model to the experimental data for deposited film thickness vs. pulse time of each reactant gas, an optimum deposition cycle for the maximum throughput can be designed. In order to evaluate the combined kinetic model, it has been applied to TiN-ALD on a SiO2 substrate using tetrakis(dimethylamido)titanium (TDMAT) and NH3 as reactants. The existence of the transient regime is confirmed from the experimental results, which show a nonlinear dependence of the TiN film thickness on the number of deposition cycles during the initial stage. A combined kinetic model, allows film thickness values less than 10 nm to be predicted accurately. Optimized deposition cycles of TDMAT and NH3 are designed as a function of the number of deposition cycles in the transient as well as converged regions. (C) 2001 The Electrochemical Society.